Integrated certification-calibration system for a testing system having multiple test instruments

ABSTRACT

An integrated certification-calibration system for a test system having multiple test instruments is disclosed. The system of this invention is used for certifying and calibrating processor-controllable test instruments that are arranged in at least two groups of separate test instruments, where each group has a separate system controller for controlling the test instruments associated therewith. The system of this invention includes a portable certification cart containing a number of processor-controllable certification instruments for certifying the various test instruments. Interconnection cables are provided for selectively interconnecting the individual group sof test instruments to the certification instruments and for connecting the system controllers associated therewith to the certification instruments. Each system controller has a certification executive that, when executed, controls both the test instruments associated therewith and the certification instruments so that certification tests are run on the test instruments. Test instruments that are processor-calibratable are calibrated by the system controller when they fail certification testing.

FIELD OF THE INVENTION

This invention relates generally to the field of metrology, and, morespecifically, to an integrated certification-calibration system forproviding an indication of the accuracy of a number of different testinstruments and for calibrating same.

BACKGROUND OF THE INVENTION

An integral part of functionally testing modern technical equipment isverifying, or certifying, that the test instruments used to make thefunctional tests operate properly and within their rated accuracy. Testinstruments used to generate stimuli to equipment under test must becertified to ensure that the desired stimuli are, in fact, produced.Test instruments used to measure the response of equipment under testmust be certified to ensure that equipment responses are accuratelyquantified or qualified. If either type of test instrument fails tofunction properly, the functional testing process in which theinstruments are used may be faulty. The functional testing could producetest results indicating that a portion of some equipment ismalfunctioning, when in fact, it is not, or alternatively indicatingthat a portion of the equipment operates properly when the opposite istrue.

A process related to instrument certification is calibration.Calibration is the process of adjusting components on test instrumentsso that the instruments either deliver appropriate stimuli or makeaccurate measurements, and/or determining appropriate corrections to beapplied to the instruments. Certification and calibration are usuallyperformed together as an iterative process. If an instrument fails acertification test, it is calibrated. The instrument is then subjectedto another certification test. In this manner, an instrument isrepeatedly subjected to certification testing and calibrated until iteither passes certification or is deemed unusable.

Calibrating and certifying the instruments used to functionally testaircraft and other complex equipment is a difficult task. An aircraft,for example, comprises a number of different systems, each of which isdesigned to perform a general function. Each system is usually made upof separate subsystems comprising numerous components designed toperform a specific task. Manufacturing, maintenance, safety, andregulatory requirements demand that the individual components andsubsystems be subject to frequent and extensive functional testing.Functional testing of this nature requires a large number of, anddifferent types of, test instruments. Each test instrument must besubjected to a specific calibration and certification process for eachfunction the instrument performs to ensure that the instrument operatesproperly. Significant amounts of technician time are thus required toperform the individual calibration and certification processes.Moreover, the certification tests and calibrating adjustments performedon any individual instrument are inherently subject to technician error.The number of certification and calibration processes that must beperformed on large numbers of test instruments used in some environmentsincreases the likelihood that even the most conscientious technician mayimproperly calibrate and certify a given instrument.

In addition, one type of test instrument can have differentcertification requirements that depend on the specific system theinstrument is used to test. An instrument may be calibrated andcertified for test functions that are not involved in the particularfunctional testing for which the instrument will be used. At the least,this type of calibration and certification may simply result in excesstime being spent certifying the instrument. At the worst, this type ofcalibration and certification can result in a test instrument beingcertified as operational when, in fact, it may not be so certified forthe tests it is used to perform.

Instrument calibration and certification also requires that each time atest instrument is calibrated and certified, a record of the processesbe made. Calibration and certification records are used for studyingfault histories of the instruments so that the source of the faults canbe identified and corrected. Calibration and certification records arealso used for determining if a particular instrument has a fault patternthat indicates that the accuracy of the instrument for functionaltesting cannot be guaranteed. Regulatory authorities often requireinstrument certification records to be maintained so that theauthorities can verify that only properly certified test instruments areused for functional testing.

Generating and maintaining instrument calibration and certificationrecords contributes to the complexities of the calibration andcertification processes. The time required to maintain a "paper trail"of each certification test adds to the time required to calibrate andcertify each instrument. Human error can cause the results of anycertification test to be either inaccurately entered or inaccuratelytranscribed.

SUMMARY OF THE INVENTION

This invention is a new and useful integrated certification-calibrationsystem for verifying that test instruments perform properly. Should aninstrument fail certification testing, the system calibrates theinstrument until it passes certification. The system of this inventionis able to automatically certify and calibrate different testinstruments, and is further able to automatically subject a particulartest instrument to the appropriate certification and calibrationprocesses based on functional tests to be run with the instrument. Theintegrated certification-calibration system also generates and maintainsrecords of each certification test performed on the test instruments.

The integrated certification-calibration system of this inventionincludes a portable certification cart with a number of remotelycontrollable and remotely readable certification instruments thereon.The system further includes groups of test instruments that are arrangedtogether. A system controller, integral with each test instrument group,regulates the running of functional tests by the test instruments. Inthe system controller, a certification executive controls both the testinstruments and the certification instruments. The certificationexecutive contains a number of certification routines and calibrationroutines for certifying and calibrating the test functions of the testinstruments.

When it is desirable to certify a particular instrument group, thecertification cart instruments are connected to the test instruments andthe system controller. A specific certification routine or calibrationroutine for the test instrument function to be certified is then invokedfor execution by the system controller. Each certification routinecontains a set of system controller-executable instructions for runningcertification tests on a particular test instrument. The certificationroutine also includes a set of instructions directing the systemcontroller to write the results of the certification tests into memory.

Calibration routines similarly contain instructions directing the systemcontroller to run certification tests on the test instruments and towrite the test results into memory. The calibration routines alsocontain instructions that are invoked if the test instrument failscertification testing. These instructions control the test instrumentcomponents so as to adjust the operation of the instrument so it willoperate properly. Further, the calibration instructions reinvoke thecertification tests to determine if, as a result of the calibratingadjustments, the test instrument operates properly.

The certification-calibration system simplifies the certification andcalibration of instruments used for functional testing. Thecertification and calibration routines run on the system controller foreach group of test instruments perform the instrument certification andcalibration with little or no technician assistance. The system thusminimizes the technician time required to certify the instruments, andsubstantially reduces the probability that human error will cause aparticular instrument certification or calibration process to beperformed inaccurately.

The certification and calibration routines for a test instrument groupis designed to run only the certification and calibration procedures forthe test instrument test functions used in the functional testing thatthe group performs. This approach ensures the appropriate test functionsof each test instrument in the group are calibrated and certified.Moreover, needless certification testing and calibration of unused testfunctions of the test instruments in each instrument group areeliminated.

Another advantage of this system is that new certification andcalibration routines with additional or substituted certification orcalibration procedures for the test instruments can be readily enteredinto the system controller. Whenever the test instrument test functionsused for a particular set of functional tests change, new certificationor calibration procedures for the updated functions are simply loadedinto the system controller. This capability eliminates the need to teachtechnicians new certification or calibration procedures each timeinstrument test functions used in the functional testing change.Furthermore, since the certification and calibration routines areassociated with the instrument groups rather than the certificationcart, there is no need to take the cart out of service each time it isnecessary to update the routines.

A further advantage of this system is that the results of certificationtesting are automatically recorded and maintained by the systemcontroller. Technician time and administrative overhead required togenerate and maintain a paper trail of certification and calibrationrecords for each instrument are essentially eliminated. Since therecording and archiving of the certification test results are performedautomatically, the possibility that human error can cause inaccuratecertification records to be archived is similarly eliminated.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be pointed out with particularity in the appendedclaims. The above and further advantages of the invention may be betterunderstood by referring to the following detailed description taken inconjunction with the accompanying drawings in which:

FIG. 1 is a general diagrammatic block diagram of an integrated testsystem incorporating a calibration system constructed in accordance withthe invention;

FIG. 2 is a block diagram of an automated test equipment cart and acertification cart that is part of the integrated calibration system ofFIG. 1;

FIG. 3 is a block diagram of a system controller of an automated testequipment cart of FIG. 2 wherein individual routines that control thecertification and calibration of instruments on the automatic testequipment cart in accordance with this invention are depicted asseparate modules;

FIGS. 4a-b are block diagrams that show the subparts of a certificationroutine and a calibration routine of this invention as separate modules;

FIG. 5 is a block diagram of the tool library and driver library of thecertification executive depicted in FIG. 3, wherein individual tools anddrivers that control the test instruments and certification instrumentsin accordance with this invention are depicted as separate modules;

FIG. 6 is a flow chart or process diagram of how an instrumentcertification procedure is performed in accordance with the instructionscontained in a certification routine of this invention;

FIG. 7 is a flow chart or process diagram of how an instrumentcertification and calibration procedure is performed in accordance witha certification and calibration routine of this invention; and

FIG. 8 is a block diagram of a portion of the system controller memorywherein checker routines that indicate whether the routines that controlthe automated test equipment cart instruments are depicted as separatemodules.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 depicts an integrated test system 10 for performing functionaltests on an aircraft 11, which includes a certification-calibrationsystem 12 constructed in accordance with this invention to verify theaccuracy of test instruments used on the aircraft 11. The integratedtest system 10 includes a number of automated test equipment carts(ATEs) 14, 16, 18, and 20, each of which contains test instruments forfunctionally testing a specific system on the aircraft 11. A centralcontrol unit 22, a main computer, is provided for selectively loadingprograms and information into the ATEs 14-20, and for retrievinginformation therefrom. Information retrieved from the ATEs 14-20 isstored by the central control unit 22 in a memory file 24 from which theinformation can be selectively accessed.

Each ATE 14-20 carries a number of test instruments that are designed toprovide input stimuli or make measurements that are required to testspecific components and subsystems on the aircraft 11. Specifically, ATE14 includes test instruments for testing the flight controller system ofthe aircraft 11; ATE 16 includes test instruments for testing theavionics system of the aircraft 11; ATE 18 includes test instruments forsimulating the engines of the aircraft so that the engine systems can betested; and ATE 20 includes power supplies for testing the electricaland power systems of the aircraft 11. As depicted by communications link26, shown partially in solid and partially in phantom, each ATE 14-18 or20 is selectively connected to the aircraft 11 so that the testsperformed by the ATE can be run. As the testing of aircraft 11progresses, the connected ATE 14-18 or 20 internally stores the resultsof the tests. After an ATE 14-18 or 20 is used to run tests on one ormore aircraft 11, the ATE is then connected to the central control unit22 by a communications link 30, shown partially in solid and partiallyin phantom. The central control unit 22 then retrieves the testinformation for the aircraft 11 from the ATE permanent memory 24. TheATEs 14-20 can be used to run tests on specific systems in the aircraft11 at any time during the manufacture of the aircraft, or duringsubsequent maintenance inspections.

Referring to FIG. 2, engine simulator ATE 18 (and test instruments 32-46included therein) are shown and described below as being representativeof each of the ATEs 14-20. The ATE 18 includes two digital multimeters32 and 33, respectively, for measuring resistances, voltages, andcurrents. A frequency counter 34 provides a measure of the outputfrequency of any pulse or AC signals that are required. A first DC powersupply 36 provides an output voltage between 0.5 and 10 volts DC, and asecond DC power supply 38 provides an output voltage between 0.5 and 50volts DC. A variable programmable resistor 40 provides loads rangingfrom 25 to 20,000 ohms. A set of load resistors 42 provide commonly usedfixed load resistances. Function generators 44 and 45 provide a sourceof variable shape and frequency AC signals. An angle position indicator46 provides an indication of mechanical angular displacement based onthe relative voltages of two input signals. Each test instrument 32-46is processor controllable. In other words, these test instruments 32-46that make measurements do so in response to commands transmitted overdigital data processing communication links and report the results ofthe measurements over the communication links. Test instruments 32-46that generate stimuli do so in response to commands received overdigital data processing communication links.

Test instruments 32-46 are connected to aircraft 11 over one or moresignal interface cables 47. The head of the signal interface cable 47has a number of individual pin connectors, not illustrated, that provideconductive links to individual circuits on the aircraft 11. A switchmatrix 48 on ATE 18 provides interconnections between terminals on thetest instruments 32-46 and the individual signal interface cable pins.Switch matrix 48, like the test instruments 32-46, is processorcontrollable.

The ATE 18 has a system controller 50 that directs the operation of theindividual test instruments 32-46. System controller 50 has akeyboard-printer 52 for bi-directionally loading instructions and data,and a display touch screen 54 for display and input of information. Thetouch screen allows a technician to enter instructions and informationinto the controller 50 by simply touching the face of the display 54 onwhich a menu of selections is provided.

FIG. 3 depicts the basic processor elements of the ATE 18 systemcontroller 50. A central processing unit 56 controls the controloperation of the ATE 18 in response to sets of program instructions. Amemory 58 is provided for storing program instructions used to run theATE and also test data 60 developed as a consequence of running the ATE18. The system controller 50 also has a number of input and outputunits, represented by block 62, so that the system controller 50 canexchange instructions and data with other elements of the integratedtest system 10. Specifically, the input/output units 62 provide forinformation exchange with the aircraft 11, the central control unit 22,the test instruments 32-46, the keyboard printer 52, the display touchscreen 54, and a certification cart 100 (FIG. 1) to be describedhereinafter. One or more communication buses 64, one shown, connectedbetween the central processing unit 56, the memory 58, and theinput/output units 62 allow for the exchange of informationtherebetween.

The specific programs that control the operation of the ATE 18 aredepicted as modules inside the system controller memory 58. An operatingsystem 66 serves as a housekeeping controller for the ATE 18. Theoperating system 66 controls the operation of the ATE 18 when firstinitialized, and is used to store and maintain operating informationmaintained by the ATE 18. An example of the type of information that theoperating system 66 maintaings is the serial numbers of the instruments32-46 that are in the ATE 18. A test executive 68 controls the testinstruments 32-46, and allows a technician to manually control same. TheATE 18 is also controlled by a number of test applications 70, 71, and72. Each test application 70-72 is a set of system controller-executableinstructions that causes ATE 18 to automatically perform a specificfunctional test on a component or subsystem of aircraft 11. Testapplications 70-72 include instructions that direct the results of thefunctional testing to be written into the memory 58 as test data 60.

System controller 50 also includes a tool library 74 and a driverlibrary 76. Tool library 74 contains a number of instrument tools (notdepicted), each of which is a set of general instructions for performinga specific task with a test instrument 32-48 or the switch matrix 49.Driver library 76 contains a number of individual drivers (notdepicted), that are specific instructions responded to by testinstruments 32-48 and the switch matrix 49. Tools are invoked forexecution by the test executive 68 or by test applications 70-72 toperform a general instrument-related task. Drivers are invoked by thetools to actually manipulate the appropriate test instruments and theswitch matrix.

After system controller 50 is initialized, operating system 66 (FIG. 3)invokes test executive 68 to run ATE 18 as represented by arrow 91. Thetest executive 68 can then be used by the technician to control the testinstruments 32-46 and switch matrix 48 by directly invoking, asrepresented by arrow 92, directed to the tool library 74. Alternatively,test executive 68 can be used to invoke one of the test applicationsthat automatically performs a functional test, as represented by arrow93, directed to test application 71. Test application 72 then accessesthe tool library 74, as represented by arrow 95, so that appropriateinstrument tools for the desired functional test are invoked. Theinvoked instrument tools execute the appropriate instrument drivers asrepresented by arrow 97. Test application 71 also directs the testresults to be written into memory 58 as test data, connection not shown.

The test executive 68, the test applications 70-72, the tool library 74and the driver library 76 are collectively developed at test developmentsites 78 and 80 (FIG. 1), which are connected to the central controlunit 22. The programs 68-76 are downloaded into the ATE systemcontroller 50 through the central control unit 22. The central controlunit 22 also maintains a copy of the programs 66-84 in memory file 24.

When the ATE 18 is used to test a specific subsystem of the aircraft 11,the ATE is connected to the aircraft by the signal interface cable 47.One or more of the test applications 70, 71 or 72 can then beselectively run on the system controller 50 so that the ATE 18 will, inturn, automatically perform functional tests on the aircraft 11. Anyfunctional test of the aircraft 11 may involve the generation of one ormore stimulus signals for input into the aircraft and monitoring aresponse to the stimulus from one or more output lines. The results ofthe test are then stored as test data 60 in the memory 58. After thetesting of the aircraft 11 is completed, the ATE 18 may be connected tothe central control unit 22 by communications link 30. The centralcontrol unit 22 copies the test data 60 from the memory 58 into thestorage file 24 to permanently archive the test results for futurereference.

The other ATEs 14, 16, and 20 function in the same general manner as ATE18. Each ATE 14-20 has a different set and number of test instruments32-48 designed to run functional tests on the components and subsystemscomprising a specific system of the aircraft. The programs 66-84 runningon each ATE 14-20 are custom designed for the specific functional testsperformed by the ATE and the test instruments thereon.

The integrated certification-calibration system 12 of this invention isused to certify that ATE test instruments 32-46 operate within theperformance levels required to run functional tests on the aircraft 11.Test instruments 32-46 that are designed to apply an input stimulus tothe aircraft 11, for example function generators 44 and 45, are checkedto certify that the instruments generate the desired signals. Testinstruments 32-46 that quantitatively measure signals from the aircraft11, for example digital multimeters 32 and 33, are checked to certifythat they provide accurate measurements. The integrated calibrationsystem 12 includes the portable certification cart 100 (FIG. 1) thatcontains a number of certification instruments 104-116. System 12 alsoincludes a certification executive 102 that is run on system controller50 (FIG. 3). Certification executive 102 controls both the testinstruments 32-46, and certification instruments 104-116 so that thelatter automatically certify the former. Certification executive 102also contains instructions that direct the system controller 50 tocalibrate or adjust test instruments 32-46 that fail certificationtesting. A test instrument site, represented by terminal 103, which isconnected to the central control unit 22 is also provided. The testinstrument site terminal 103 is located a test instrument repairfacility allows instrument technicians to review and update the recordsof instruments used for functional testing.

With this background, the integrated certification-calibration system 12may be better understood by reference to FIG. 2, which depicts thecertification cart 100 and certification instruments 104-116 thereon.Certification cart 100 has both a function generator 104 and a frequencycounter 105. A calibrator 106 serves as a very precise voltage andresistance source. A syncro-resolver simulator 107 generates signalsthat simulate those normally received by an angle-position indicator.Certification cart 100 also has an angle position indicator 108. A phaseangle volt meter 109 provides phase angle and voltage measurements.Certification cart 100 further carries a DMM 112. There is also anon-cart ARINC bus analyzer 116 which is used to monitor digitallyencoded data exchanged between aircraft internal components and the ATEs14-20. Each of the certification cart instruments 104-116 is like testinstruments 32-46, processor controllable.

An on-cart receiver board 117 and a removable interface test adapter 118facilitate the interconnection of the test instruments 32-46 andcertification instruments 104-116. The certification instruments 104-116are each connected to terminals, not shown, on the receiver board 117.The interface test adapter 118 connector is designed for connection atone end to the receiver board 117 terminals. The other end of theinterface test adapter 118 has a socket, not illustrated, to which ATE18 signal interface cable is connected. When an ATE 14, 16 or 20 havinga different type of signal interface cable is connected to thecertification cart 100, an interface test adapter with the appropriatecomplementary signal interface cable socket is attached to the receiverboard 117. A processor controllable switch matrix 119 controls theinterconnections of certification instruments 104-116 to the receiverboard 117 terminals.

An instrument bus 124 attached to ATE 18 provides a path for theexchange of digital data processing signals between the ATE systemcontroller 50 and the certification instruments 104-116 and the switchmatrix 119. In the depicted embodiment, instrument bus 124 is coupledinto a complementary socket, not illustrated, on the interface testadapter 118. The interface test adapter 118, the receiver board 117 andthe certification cart 100 are each provided with appropriate terminalsand conductors that establish digital data processing signal pathsbetween the certification instruments 104-116 and the instrument bus124.

Certification executive 102 includes a menu/controller 120 that runs onthe system controller 50 as depicted in FIG. 3. As represented by arrow121, operating system 66 calls menu/controller 120 for execution whencertification executive 102 is first invoked. Menu/controller 120 can beused by technicians to manually control test instruments 32-46,certification instruments 104-116, and switch matrices 48 and 119. Themenu/controller 120 also allows the technician to store or retrieve testresults 60.

Certification executive 102 also includes a number of certificationroutines 122 and 124 and calibration routines 126 and 128 that aresystem controller 50-executable instructions used in performingcertification and calibration procedures on test instruments 32-46.Individual certification routines 122 and 124 and calibration routines126 and 128 are executed by system controller 50 in response toinvocation calls made by menu/controller 120 as represented by an arrow130 directed to certification routine 122. Certification routines 122and 124 are run to certify test instruments 32-48 that are not adaptedto be remotely calibrated. Calibration routines 126 and 128 are run tocertify and calibrate test instruments 32-48 that are capable of beingremotely calibrated. In the described embodiment of the system 12, onlytwo certification routines 122 and 124 and two calibration routines 126and 128 are shown. However, it is readily understood that the systemcontroller 50 has as many certification and calibration routines 122-128as are required to certify and calibrate the test instrument testfunctions used during the functional testing performed by ATE 18.

Certification routine 122 is represented in greater detail in FIG. 4a asbeing representative of the certification routines 122 and 124. Thecertification routine 122 contains a set of initialization instructions134, a set of certification instructions 136, and a set of range values138. Initialization instructions 134 direct system controller 50 toprepare ATE 18 and certification cart 100 for certification andcalibration procedures. For example, initialization instructions 134direct the system controller 50 to generate a number of messages ondisplay touch screen 54 that direct and inform the technician whatpreparatory steps need to be taken prior to performing the certificationprocess on any test instrument 32-48. The initialization instructions134 may, for example, include instructions to turn on selectedcertification instruments 104-116.

Certification instructions 136 are executed by the system controller 50to perform the certification of the test instruments 32-46 or 48. Thecertification instructions 136 are the instructions that control thetest instruments 32-48, the certification instruments 104-116, andswitch matrices 48 and 119 so that the test instrument can be certified.During the running of the certification instructions 136, the rangevalues 138 are referenced to obtain the acceptable performance standardsfor the function of the instrument being tested, within which theinstrument must operate in order to be considered certified. Forexample, when the resistance measuring functions of DMMs 32 and 33 aretested against a 100 ohm standard, the acceptable indicated resistancefor the multimeters should be between 98.5 and 101.5 ohms.

Calibration routine 126 is depicted in greater detail in FIG. 4b asbeing representative of the calibration routines 126 and 128. Thecalibration routine 126 contains initialization instructions 140,certification instructions 142, and range values 144 that are the sameas the initialization instructions 134, the certification instructions136, and range values 138 of certification routine 122. Calibrationroutine 126 includes a set of calibration instructions 146 that areexecuted by system controller 50 to calibrate a test instrument 32-45 or46. As represented by bidirectional arrow 148, calibration instructions146 are invoked in response to an indication that the test instrumentfailed certification testing. After the calibration instructions 140 areexecuted, the certification instructions 142 are then reinvoked todetermine if the calibration process was successful.

It should be understood that in the foregoing description, depiction ofthe initialization instructions 134 and 140, the certificationinstructions 136 and 142, the range values 138 and 144, and thecalibration instructions 146 as separate modules was for the purposes ofillustration only. In any particular certification or calibrationroutine 122-126 or 128, the separate subsets of instructions thatcomprise the routine may be integrated together as necessary. Forexample, the range values 138 and 144 are typically integrated into theassociated certification instructions.

Certification executive 102 also contains a tool library 150 and adriver library 152, both depicted in greater detail in FIG. 5. Toollibrary 150 contains a number of instrument tools 154-156, each of whichis a general set of instructions for performing tasks with either thetest instruments 32-48, the certification instruments 104-116, or theswitch matrices 48 and 119. Instrument tool 154, for example, is a setof general instructions that direct DMM 32 on the ATE 18 to make aresistance reading. Instrument tool 159 is a set of general instructionsthat directs the certification cart 100 function generator 104 togenerate a particular type of AC signal. The instrument tools 154-156that control the ATE test instruments 32-48 and switch matrix 48 areidentical to the instrument tools in the tool library 74 as accessed bythe test executive 68 and test applications 70-72.

Driver library 152 contains a number of individual drivers 162-166 thatare specific instructions responded to by the test instruments 32-48,the certification instruments 104-116, and switch matrices 48 and 119.Drivers 162-164, for example, contain instructions to which ATE 18 DMM32 responds. Drivers 167-169 comprise instructions certification cart100 function generator 104 responds to. For example, driver 167 may bean instruction to function generator 104 to generate a square wave;driver 168 may be an instruction to generate an output signal at a givenfrequency. When an instrument tool 154-159 is invoked for execution, thetool, in turn, invokes one or more drivers 162-171 to manipulate theparticular instrument or switch matrix. For example, when functiongenerator tool 159 is invoked, the tool invokes driver 167 to direct thefunction generator 104 to generate a square wave, as represented byarrow 173. Instrument tool 159 then invokes driver 168, as representedby arrow 174, to generate a square wave at a specific frequency. Whileonly a limited number of instrument tools 154-159 and drivers 162-171are shown, it should be recognized that tool library 150 and driverlibrary 152 contain a sufficient number of tools and drivers tomanipulate all of the test instruments 32-48, the certificationinstruments 104-116, and the switch matrices 48 and 119 as is required.

As depicted by arrows 176 and 178 in FIG. 3, the menu/controller 120 andthe certification and calibration routines 122-128 are each capable ofaccessing tool library 150 to control the operation of a particular testinstrument 32-46, certification instrument 104-118, or switch matrices48 and 119. Each instrument tool 154-159 invoked then executes theappropriate driver 162-171, as required.

FIG. 6 depicts in block diagram form how ATE test instruments 32-48 arecertified using this integrated calibration system 12. Certificationstarts with the "boot-up" or initialization step 180 of the ATE systemcontroller 50. Initialization 180 is performed automatically by thesystem controller 50 in response to a set of instructions contained inthe operating system 66.

During initialization 180 and throughout the certification procedure,system controller 50 generates messages on the display touch screen 54informing the technician of what steps need to be taken during thecertification process. The messages may instruct the technician toindicate that he has performed the required tasks by generating a"step-completed" message. The step-completed message is used by thesystem controller 50 as a signal to proceed with the execution of theprogram running the ATE 18 and the certification cart 100. Thestep-completed message is normally transmitted to system controller 50by the technician touching a section on the face of display touch screen54. Menus offering the technician choices during the testing process andresponses to these menu choices are similarly exchanged through displaytouch screen 54.

At the end of initialization 180, the system controller generates a menu182 informing the technician of the procedures the ATE 18 is able toperform. The procedures the ATE 18 can perform are: TEST procedures,wherein ATE 18 can be used in a test mode to perform functional tests ona specific system on the aircraft 11, and, CERTIFY-CALIBRATE procedures,wherein the ATE is run in a certification mode to certify or calibratethe test instruments 32-48. To prevent the unauthorized invocation ofthe certification and calibration routines, a password must be enteredwith this selection before the system controller 50 will proceed withthis procedure (password entry step not shown).

If the CERTIFY-CALIBRATE procedures option is selected, thecertification executive 102 is invoked for execution 184 by operatingsystem 66. The menu-controller 120 is initially executed and directs thesystem controller 50 to generate a menu 186 allowing the technician toselect the ATE instrument 32-45 or 46 to be certified. After aparticular test instrument 32-45 or 46 is selected, a second menu 188may then be generated requesting the technician to select the functionof the selected instrument to be certified or calibrated. For example,if a technician selects DMM 32 for certification, a second menu directsthe technician to select the DC voltage, the AC voltage, the resistance,or the current measuring capability of the meter for certification.Menu/controller 120 also allows the technician to select a manualtesting mode, not illustrated, wherein the technician can directlycontrol the test instruments 32-48, the certification instruments104-116, and switch matrices 48 and 119 through the system controller50.

In response to the selection of the specific test instrument 32-45 or 46and instrument function to be certified, the system controller 50performs an invocation step 190 and calls the appropriate certificationor calibration routine 122-126 or 128. In the depicted process,certification routine 122, a DC voltage certification routine used tocertify the DMM 32, is invoked for execution. The initializationinstructions 134 are the first part of routine 122 executed. Theinitialization instructions 134 direct system controller 50 to execute apreparation step 192 that readies the ATE 18 and the certification cart100 for the actual certification process. The preparation step 192includes placing the test instrument and appropriate certificationinstruments 104-116 in the appropriate state for certification of thetest instrument. Certification initialization instructions 134 incertification routine 122 includes instructions to prepare DMM 32 totake voltage measurements and to prepare the certification cart 100calibrator 106 to generate precise voltages. The DMM 32 and thecalibrator 106 are manipulated for the certification process byexecution of the appropriate instrument tools 159-161 and drivers162-171.

Initialization instructions 134 may also direct system controller 50 togenerate messages 194 informing the technician of the steps necessaryfor the certification process to proceed. The messages may, for example,include instructions directing the technician to turn on and setselected test instruments 32-46 and selected certification instruments104-116, and to make appropriate signal interface cable 48 andinstrument bus 124 connections between the ATE 18 and the certificationcart 100.

System controller 50 then performs an initialization complete check 196.Initialization complete check 196 comprises a number of internal selftests that verify that the certification procedure can be run. Theinternal self tests include verifying that the appropriate connectionshave been made between the ATE 18 and the certification cart 100. Theself tests also include verifying that the certification instruments104-116 are set to the appropriate states for the certification of thetest instrument 32-45 or 46. If the initialization self checks indicatean unsuccessful initialization, remedial initialization steps 198 areperformed. Remedial steps 195 include additional internal commands tothe test instruments 32-44 or the certification instruments 104-116 toplace the instruments in the proper state for the certification process.Remedial steps 195 further include generating messages directing thetechnician to perform the necessary corrective processes to place theATE 18 and the certification cart 100 in a preparatory state for thecertification process. As the remedial steps 195 are performed, theinitialization self check 196 may be concurrently performed therewith asrepresented by a bi-direction arrow 197.

After the results of the initialization self test 196 indicate that thecertification procedure can proceed, system controller 50 performs aninvocation step 198 that calls the certification instructions 136 forexecution. The certification instructions 136 direct the systemcontroller 50 to perform a number of certification tests represented byblocks 200-208.

As illustrated by way of example for certification test 200, eachcertification test includes a perform test step 210. The perform teststep 210 for the initial certification test 200 includes setting theswitch matrices 48 and 119 so that the test instrument being certifiedis connected to the appropriate certification instruments 104-116. Theperform test step 210 for the initial certification test 200 and each ofthe subsequent certification tests 200-208 includes making acertification test and storing the results of the test in memory 58 astest data 60. When the DC voltage measurement function of DMM 32 istested, the initial perform test step 210 is made by supplying astandard or reference 0.5 volt DC signal from the calibrator 106 to theDMM 32 or 33 for measurement by the latter.

After the perform test 210, a certification comparison 212 is carriedout. Certification comparison 212 includes the step of comparing theresults of the certification test 210 to the range values 138 for thetest to determine whether the involved test instrument 32-45 or 46functions within allowable limits so that it can be considered certifiedfor the purposes intended. The certification comparison 212, whichfollows the 0.5 DC volt perform test 210, comprises the step ofdetermining if the multimeter made a DC voltage measurement of between0.49 and 0.51 volts DC.

If the certification comparison 212 indicates that the test instrumentwas not functioning within its rated tolerance, a flag set step 214 isperformed. Flag set step 214 comprises the setting of one or more flagsindicating that the test instrument being certified failed thecertification test 200. The flag set may include a message on either thekeyboard-printer 52 or the display touch screen 54. The flag set step214 may also include setting an internal flag within the systemcontroller 50. For example, a flag may be set by the operating system 66indicating that the particular instrument failed the certification test200. Depending on the construction of the operating system 66, thesystem controller 50 may, in response to the set failure flag, inhibituse of the test instrument during functional testing.

After each certification test is complete, for example certificationtest 200, the certification procedure proceeds to the next certificationtest 202. The next performed test step is performed at a differentinstrument performance level than the previous perform test step 210 andthe certification comparison is between a different range of tolerancevalues than those in certification comparison 212.

The number of certification test steps 200-208 performed by a particularcertification routine 122 or 124 depends on the particular certificationrequirements of the function of the test instrument 32-45 or 46 beingcertified. The DC voltage measurement function of the DMM 32 is testedat 0.5, 1, 2, 3, 10, 28, 50, 100, 150, 200 and 250 volts. The DMM 32 isalso certified for appropriate negative voltages in addition to theabove-listed positive voltages. These certification tests verify thatthe voltmeter is measuring voltage signals within its rated accuracythroughout the range that the meter is used.

Certification tests 200-208 are also performed at levels and usingfunctions provided by the particular test instrument 32-45 or 46 when itis used on the specific ATE 14, 16, 18, or 20. Test instruments 32-46that generate stimuli signals are subjected to certification tests200-208 at commonly used output levels. Test instruments 32-46 thatmeasure output signals are subjected to certification tests 200-208 atsignal levels the instruments commonly measure during the testingprocess. The DMM 32 on the engine simultor ATE 18, for example, isfrequently used to test a 28 VDC signal on the aircraft 11 enginesystem. Accordingly, certification procedure 122 for DMM 32 includes acertification test to verify that the meter can accurately measure 28VDC.

At the conclusion of the perform test step for the last certificationtest 208 (perform test step not illustrated), the switch matrices areopened so that the test instrument 32-45 or 46 is disconnected from thecertification instruments 104-116. This minimizes the possibility that aspurious signal may damage any of the instruments 32-46 or 104-116.

After certification tests 200-208 have been completed, there is a printstep 216 during which the test results are printed on thekeyboard-printer 52. The printed results typically take the form of aheader message identifying the specific test instrument 32-45 or 46tested and the particular test function of the instrument tested. Themessage includes a listing of the particular level at which theinstrument was tested, the results of the test, and the rated tolerancerange for the instrument at that level. A flag message indicating thatthe test instrument 32-46 or 48 failed a particular certification test200-206 or 208 is also printed out with the results of the certificationtest. Alternatively the certification test results may be printed aspart of the perform test steps.

After certification test 200-208 have been run, certification routine122 performs an end procedure 218. End procedure 218 comprisesgenerating a message informing the technician that the certificationprocess performed by the routine has been completed. An invocation step220, recalling the menu/controller 120 is then reinvoked to run the ATE18 and the certification cart 100 is then performed.

A menu 222 is generated, offering the technician a selection ofprocedures that can next be performed. The procedures that can next beperformed include: re-executing the just performed routine 122 oranother test function of the same test instrument 32-45 or 46;certifying or calibrating another test instrument; or, leaving theCERTIFY-CALIBRATE mode. If the latter option is selected, acertification exit step 224 is performed. The certification exit step224 includes the generation of messages instructing the technician howto unhook ATE 18 from certification cart 100 and the invocation of theoperating system 66 to control the ATE 18.

The certification procedure depicted in FIG. 6 also includes unloadingthe results of the certification tests 200-208 to central control unit22 for archival in storage file 24. The unloading of the test resultsbegins by connecting the ATE 18 to the central control unit 22 by way ofthe communications link 30, represented by block 226. After the ATE 18and the central control unit 22 are interconnected, the central controlunit 22 interrogates and reads in block 228 the test data 60 from systemcontroller memory 58. During the interrogation and read 228, the resultsof certification tests 200-208 from executed certification andcalibration routines 122-128 that are stored in the memory 58 are copiedinto the storage file 24.

FIG. 7 depicts in block diagram form how a calibration routine 126 isinvoked to calibrate a test instrument, for example, function generator44. The initial steps of the calibration procedure, including invocationof the calibration routine 126, are identical to steps 180-198 performedduring execution of the certification routine 122 described withreference to FIG. 6 and will not be described again. As depicted in FIG.7, certification instructions 142, range values 144, and calibrationinstructions 146 are integrated to form a number of calibration tests240-248. As illustrated by way of example for calibration tests 240 and242, each test includes certification tests 250 and 252 followed bycertification comparisons 254 and 256, respectively. Certification tests250 and 252 are substantially identical to the perform test step 210 ofthe certification procedure 122; certification comparisons 254 and 256are substantially identical to the certification comparison 212 of thecertification procedure. The specific certification tests 250 and 252performed on the function generator 44 or 45 include directing thefunction generator to generate an AC signal at a specific frequency andmeasuring the signal with a certification cart frequency counter 106.

As depicted with respect to calibration test 240, if the certificationcomparison 254 indicates the instrument is not functioning withinallowable or rated accuracy limits, the calibration instructions 146 areinvoked and a failure counter incrementation step 258 is performed.Failure counter incrementation step 258 includes the step ofincrementing a cumulative calibration test counter that is establishedby calibration routine 126 to record the number of times the functiongenerator 44 failed one of the calibration tests 240-248. Failurecounter incrementation step 258 also includes incrementing an individualcalibration test counter, also established by calibration routine 126,that records the number of times the function generator 44 failed aparticular calibration test 240-246 or 248.

Following failure count incrementation step 258 is a failure countcomparison 260. Failure count comparison 260 includes the steps ofreading the contents of the cumulative calibration test counter todetermine if the function generator failed the calibration tests 240-248more than a predefined number of times. The step also includes readingthe contents of the individual calibration test counter to determine if,for example, the function generator 44 failed calibration test 240 morethan a predefined number of times. If there are either excess failuresof the total calibration tests or of an individual calibration test, aflag set step 262 is performed. Flag set step 262 includes the settingof one or more flags to indicate that attempts at calibrating theout-of-certification function generation were unsuccessful. The flagsset by the flag set step 262 are similar to the flags set during theflag set step 214 that is executed during the running of certificationroutine 122.

If the failure count comparison 260 indicates that less than thepredefined number of total calibration tests 240-248 of a particularcalibration test have occurred, calibration routine 126 proceeds to acalibration step 264. Calibration step 264 involves the steps ofgenerating the appropriate calibration commands to a balancing componentwithin the function generator 44 so as to adjust the output of thefunction generator. Following calibration 264 certification test 250 andcertification comparison 254 are repeated.

When the function generator 44 passes the certification comparison 254the calibration procedure proceeds to a certification test 252 andcertification comparison 256 of calibration test 242. The individualcalibration test counter for calibration test 240 may also be zeroed(step not shown). Calibration test 242 includes a failure countincrementation step 266, a failure counter comparison step 268, and aflag set step 269 identical to the same steps described with respect tocalibration test 240. Calibration test 242 further includes acalibration step 270 that, like calibration step 264, comprises thegeneration of commands to a balancing component inside functiongenerator 44 so as to calibrate it.

Following calibration step 270, the certification procedure performed bycalibration routine 126 returns to the initial calibration test 240 andthe certification test 250 performed therein. In other words, after eachcalibration 264 or 270 is performed on function generator 44,certification tests 250 and 252 are again each performed. The repetitiveexecution of the certification test 250 and certification comparison 254after each calibration step is done to verify that the calibration offunction generator 44 at one certification point does not result in theinstrument drifting out of certification at another point. Thecalibration tests 240-248 are thus performed iteratively in order toensure that the function generator 44 operates properly throughout itsintended range of use.

At the conclusion of the execution of calibration routine 126, controlof the ATE 18 and certification cart 100 is returned to thecertification executive in a manner similar to that previously describedin steps 216-230 performed during the certification procedure run bycertification routine 122 (FIG. 6).

After instrument certification and calibration has been completed,personnel in the test instrument repair facility can review theinstrument certification and calibration records through the testinstrument site terminal 103 (FIG. 1). These records enable theinstrument technicians to determine the nature of any repair work thatneeds to be performed on the test instruments.

The test instrument tools 154-156 and test instrument drivers 162-166(FIG. 5) used during the certification and calibration procedures areidentical to the tools and drivers in the tool library 74 and driverlibrary 76 that are accessed by the test executive 68 and testapplications 70-72 (FIG. 3). Accordingly, successful certification ofthe test instruments 32-48 inherently means that the tools and driversused to manipulate the test instruments are functioning properly.

The integrated certification-calibration system 12 of this inventionalso contains a set of routines as depicted by FIG. 8 for generating anindication of whenever the test executive 68 or one of the testapplications 70-72 invoke an instrument tool or driver that has beenupdated but has not been certified. The system 12 includes acalibration-date file 290 which is maintained by part of the operatingsystem 66. The calibration-date file 290 contains a list of the dates onwhich the individual tools and drivers in the libraries 74 and 76 werelast updated, and an indication of the byte length of the individualtools and drivers. This information is updated by a test instructionupdate service 292, which is part of the operating system 66. Asrepresented by arrow 294, the test instruction update service 292 writesthe entry date and memory length information into the calibration-datefile whenever the tool library 74 or driver library 76 is updated.

The calibration-date file 290 also maintains a list of the write date ofthe last certification or calibration involving each tool or driver, andthe byte length of tool or driver when calibrated. This information isupdated by an update service 296 in the certification executive 102. Theupdate service 296 writes this information into the calibration-datefile 290, as represented by arrow 298, after a certification routine orcalibration routine has been executed (connection to certificationroutines and calibration routines not shown). This information iswritten by the update service 296 by reading the date and memory lengthinformation of the tools and drivers associated with the testinstruments that were certified or calibrated.

Whenever the test executive 68 or one of the test applications 70-72invoke a tool or driver in the libraries 74 or 76, a date checker 300 isinitially invoked (connection not shown). The date checker 300, which ispart of the test executive 68, ascertains whether the invoked tools anddrivers have been certified. The date checker 300 makes thedetermination regarding the certification of the tool or driver bycomparing the date and length of the last entered tool or driver withthe date and length of the last certified tool and driver, asrepresented by arrow 302.

If the comparisons indicate different dates or memory lengths, it isconsidered an indication that the current tool or driver which thesystem controller 50 intends to invoke has not been certified. In thissituation, the date checker 300 generates a warning notice on thedisplay touch screen 54 that the needed tools or drivers are notcertified. In order for the test technician to proceed with the intendedfunctional test, he/she must signal to the system controller 50 that thewarning has been acknowledged. The date checker 300 then allows thesystem controller 50 to proceed with the invocation of the selectedtools and drivers. In the event the comparisons indicate identical datesand memory lengths, it is considered an indication that the current toolor driver has been certified. The date checker 300 allows the invocationof the tool or driver to proceed without the display of any additionalinformation.

The integrated certification-calibration system 12 facilitates theefficient certification and calibration of large numbers of differenttest instruments 32-46. The certification routines 122 and 124 andcalibration routines 126 and 128 run on the ATE system controller 50certify and calibrate the test instruments 32-46 automatically withlittle or no technician assistance. Since technician involvement in thecertification and calibration procedures is minimized, the level oftechnician support needed to perform these procedures and thepossibility of technician error causing one of the procedures to beimproperly performed is reduced. Furthermore, there are many instanceswherein a certification routine 122 or 124, or calibration routine 126or 128 can perform a certification or calibration procedure faster thanthe most efficient technician.

The certification routines 122 and 124 and calibration routines 126 and128 integral with each ATE 14-20 are custom designed to only certifytest instruments 32-46 for the functions required by the tests the ATEis designed to perform on the aircraft. This feature eliminates needlesscertification and calibration of each test instrument for each functionof each test instrument, regardless of whether the function is used, andsubstantially reduces the possibility that any individual testinstrument may inadvertently not be calibrated and certified for aparticular test function that the instrument is required to perform.

The certification-calibration system 12 automatically archives theresults of certification tests in a storage file 24. This eliminates theneed to have a separate "paper trail", or certification records for theindividual test instruments 32-46. Automatic archival of certificationdata essentially nullifies the possibility that human error can causecertification data for a test instrument to be incorrectly recorded orstored. Furthermore, the time spent making the certification records,transcribing them and storing them is minimized. Moreover, thecertification records for each test instrument 32-46 can be readilyaccessed from the storage file 24 through a terminal connected to thecentral control unit 22 by instrument repair technicians, regulatoryinspectors, and others requiring access to the information containedtherein.

Another advantage of the certification-calibration system 12 is that itreadily allows for changes in the certification requirements andcalibration instructions of any test instrument on one of the ATEs14-20. Such changes may be required if, for example, test instrumentsused on any ATE are changed, or the function and range of use for anyparticular test instrument is changed. All that is required to modifythe certification or calibration procedure for the test instrument is tomake the appropriate changes to the certification routine 122 or 124 orcalibration routine 126 or 128 in the ATE 14-20 in which the testinstrument is installed. If the test procedure that controls the use ofthe test instruments is changed, the certification or calibrationroutine for the test instrument can be changed at the same time bysimply adding a new or modified routine to the ATE from a testdevelopment site 78 through the central control unit 22. Since thecertification and calibration routines 122-128 are provided with theATEs 14-20, there is no need to take the certification cart 100 out ofservice each time it is necessary to change a certification orcalibration routine.

The certification-calibration system 12 also inherently certifies thesoftware tools and drivers that control the test instruments. If thetools and drivers have been changed and are not certified, the datechecker 300 generates a warning message so the test technician is madeaware of the software's status before functional testing is allowed toproceed.

Still another advantage of this system 12 is that the certification andcalibration routines 122-128 are in a certification executive 102 thatis separate from the test executive 68 and the test applications 70-72.This makes it possible to update the certification and calibrationroutines 122-128 without affecting the test executive or the testapplications.

The foregoing description has been limited to a specific embodiment ofthis invention. It will be apparent, however, that the invention can bepracticed in systems having diverse designs or in systems that usedifferent internal elements than those disclosed in this specification,with the attainment of some or all of the advantages of this invention.For example, it should be understood that in other embodiments of thisinvention, different certification instruments may be used to certifytest instruments different from those described in the disclosed testsystem. Similarly, it should be understood that the exact arrangement ofthe programs used to control both the test instruments and certificationinstruments may vary significantly from what has been described. Forexample, in some embodiments of the invention, it may be desirable toprovide common tool and driver libraries that are accessed both duringthe running of automated functional tests and during the running ofcertification and calibration procedures.

The steps of the certification and calibration procedures with respectto the execution of certification routine 122 and calibration routine126, respectively, were similarly described as applied in a preferredembodiment of the invention, for purposes of illustration. The specificsteps of any given certification or calibration procedure performed by acertification or calibration routine in accordance with this inventionmay vary widely from what has been described. For example, somecalibration routines may not include the steps related to determininghow many times a particular test instrument failed each certificationtest or all of the certification tests. Other certification routines maynot include the steps of returning to perform each certification testover after any particular calibration step is performed. Othercalibration routines may not perform any calibration steps until aftereach of the certification tests are performed.

Moreover, the system 12 may also be configured to provide notices ofwhen the ATEs 14-20 need to be certified. For example, in one embodimentof the invention, the central control unit 22 may have a cartcertification notice service (not illustrated). This service maintains arecord of the date each ATE 14-20 was last certified. Each ATE 14-20needs to be certified periodically, for example, every 60 days. Towardsthe end of each 60-day period for each ATE 14-20, for example, duringthe last week of the period, the cart certification notice servicearranges to have a scheduling notice broadcast as the appropriate testdevelopment site and test inspection site terminals 76, 78 and 103,respectively. The service also arranges for scheduling notices to bebroadcast on the ATE display screen 54. The scheduling notice broadcastprovides test personnel and cart scheduling personnel with a notice thata cart needs to be certified. This facilitates the orderly scheduling ofcart certification so that there will be minimum disruption of thefunctional testing process.

Therefore, it is the object of the appended claims to cover all suchmodifications and variations as come within the true spirit and scope ofthe invention.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. An integrated aircrafttest system for functionally testing a plurality of aircraft componentsand subsystems comprising:a. a plurality of automated test equipmentcarts, each of the automated test equipment carts including a pluralityof processor-controllable test instruments for performing functionaltests on specific aircraft components, said test instruments generatingsignals for application to the aircraft components and subsystems andmonitoring signals generated by the aircraft components and subsystems,and a system controller connected to said test instruments forcontrolling the functional tests performed thereby, at least two of thecarts having instruments for performing functional tests on differentaircraft components; b. a portable certification cart having a pluralityof processor-controllable certification instruments for measuring saidsignals produced by said test instruments and for produccing signalsmonitored by said test instruments; c. connection means for selectivelyinterconnecting said test instruments on each said automated testequipment cart to said certification cart certification instruments; andd. said automated test equipment cart system controllers each beingconnected to said automated test equipment cart test instrumentsassociated therewith and having an input/output unit selectivelyconnectable to said certification cart certification instruments andeach said system controller being operable to perform certificationtests on said associated test instruments by directing saidcertification instruments to measure signals produced by said associatedtest instruments and to produce signals for monitoring by said testinstruments and including means for receiving and storing the results ofsaid certification tests.
 2. The integrated aircraft test system ofclaim 1, wherein each said system controller further includes at leasttwo certification routines, each said certification routine comprising aset of system controller-executable instructions directing said systemcontroller to perform a certification test with said certificationinstruments, said certification routines containing instructionsdirecting said system controller to perform different certificationtests.
 3. The integrated aircraft test system of claim 1, wherein eachsaid automated test equipment cart has a signal interface cable forconnecting said test instruments associated therewith, at least two saidsignal interface cables having different connection means for attachmentto the aircraft and wherein said aircraft test system furtherincludes:a. a receiver board on said certification cart to which saidcertification instruments are connected; and b. a plurality of interfacetest adapters, each said interface test adapter being selectivelyattachable to said receiver board for providing an electricalinterconnection between at least one of the signal interface cables andsaid receiver board.
 4. The certification system of claim 3, furtherincluding:a processor-controllable switch matrix on said certificationcart for selectively establishing interconnections between said testinstruments on said automated test equipment cart to which saidcertification cart is connected and said certification instruments andeach said system controller being connectable to said switch matrix andoperable for controlling said electrical interconnections establishedthereby during said certification testing.
 5. The integrated aircrafttest system of claim 1, wherein each said system controller includesmeans for storing acceptable limits of said test results for each saidcertification test performed thereby, and each said system controllerbeing operative to compare results of each said certification test withsaid acceptable limits.
 6. The integrated aircraft test system of claim5, wherein each said system controller inhibits use of a test instrumentfor an aircraft functional test if said certification test results forsaid test instrument are outside of said acceptable limits.
 7. Theintegrated aircraft test system of claim 5, wherein:at least one of saidtest instruments is processor-calibratable; and said automated testequipment cart system controller associated with said at least oneprocessor-calibratable test instrument is operative to calibrate saidtest instrument when a certification test result for said testinstrument is outside said acceptable limits for said certificationtest.
 8. The integrated aircraft test system of claim 7, wherein saidautomated test equipment cart system controller, as part of said testinstrument calibration, directs said certification cart certificationinstruments to execute said certification test on saidprocessor-calibratable test instrument.
 9. The integrated aircraft testsystem of claim 1, wherein at least one said automated test equipmentcart system controller further includes at least two certificationroutines, each said certification routine comprising a set of systemcontroller-executable instructions directing said system controller toperform a certification test with said certification cart certificationinstruments on said associated automated test equipment cart testinstruments and said certification routines contain instructionsdirecting said system controller to perform different certificationtests.
 10. The integrated aircraft test system of claim 9, wherein eachsaid automated test equipment cart system controller includes aplurality of test applications, each said test application comprising aset of system controller-executable instructions directing said systemcontroller to perform a functional test with said test instruments onone of the aircraft components and subsystems, and wherein each saidautomated test equipment cart system controller contains a plurality ofsaid certification routines within a certification executive separatefrom said test applications.
 11. The integrated aircraft test system ofclaim 1, wherein at least one said automated test equipment cart systemcontroller further includes:a memory for storing a plurality of testinstrument programs for controlling said test instruments associatedwith said cart and a data file containing an indication for each saidtest instrument program as to whether said test instrument program hasbeen certified; certification update service means for revising saiddata file after each said test instrument certification test that saidtest instrument program associated with said test instrument has beencertified; and checker means for accessing said data file prior to eachsaid functional test to determine if said test instrument programassociated with said test instrument used for said functional test hasbeen certified.
 12. The integrated aircraft test system of claim 11,wherein:said data file includes an indication of when each said testinstrument program was entered into said at least one system controlleror updated, and an indication of when said test instrument associatedwith said test instrument program was last certified; said systemcontroller includes a test instrument update service means for making anentry into said data file of when each said test instrument program isentered into said system controller or updated; said certificationupdate service means writes an indication of when each said testinstrument program has been certified when each said test instrumentassociated therewith is subjected to certification testing; and saidchecker means reads said data file to compare when said test instrumentprogram was entered or updated when said test instrument program waslast certified to determine if said test instrument program associatedwith said test instrument used for said functional testing has beencertified.
 13. The integrated aircraft test system of claim 12,wherein:each said test instrument program occupies a specific amount ofsaid memory in said at least one system controller; said data fileincludes an indication of an amount of said memory each said testinstrument program occupies after said test instrument program is lastentered into said at least one said system controller or updated, and anindication of an amount of said memory each said test instrument programoccupies when said test instrument associated therewith was lastsubjected to certification testing; said system controller includes atest instrument update service means for entering into said data filesaid amount of memory each said test instrument program occupies in saidsystem controller memory when said test instrument program is lastentered or updated; said certification update service means enters intosaid data file said indication of said amount of said system controllermemory each said test instrument program occupies when said testinstrument associated therewith is subjected to certification testing;said checker means reads said data file to compare said amount of saidsystem controller memory said test instrument program occupies afterlast entry or update with said amount of said system controller memorysaid test instrument program occupies after said last certification ofsaid test instrument associated therewith to determine if said testinstrument program associated with said test instrument used for saidfunctional testing has been certified.
 14. The integrated aircraft testsystem of claim 13, wherein:said data file further includes anindication of when each said test instrument program was entered intosaid at least one said system controller or updated, and an indicationof when said test instrument associated with said test instrumentprogram was last certified; said test instrument update service meansmakes an entry into said data file of when each said instrument programis entered into said system controller or updated; said certificationupdate service means writes an indication of when each said testinstrument program has been certified when each said test instrumentassociated therewith is subjected to certification testing; and saidchecker means further reads said data file to compare when said testinstrument program was entered or updated with when said test instrumentprogram was last certified to further determine if said test instrumentprogram associated with said test instrument used for said functionaltesting has been certified.